In the continuous casting of steel billets uniform distribution of lubricant (oil) to all sides of a mold and in the proper amount is essential to insure good surface quality of the resultant casting. Insufficient supply or inadequate distribution of the lubricant may cause the steel shell near the meniscus to stick to the surface of the mold (generally made of chrome plated copper) which causes the billet being formed to be suspended momentarily in the mold and necessitates increased withdrawal forces which, in many cases, gives rise to transverse cracks and deterioration of the billet quality. On the other hand an excess supply of lubricating oil has been linked to hydrogen entrapment and pin hole formation in the billet.
Various techniques for delivering lubricant to the mold have been devised and some are currently in use, however none correlate the flow resistances through the system to insure proper distribution and uniform flow to the mold around substantially the complete perimeter of the mold.
U.S. Pat. No. 3,446,267 issued May 27, 1969 to Gricol et al discloses a system for lubricating a rectangular mold and incorporates a gap composed of a plurality of passages flaring in the direction of flow to the mold perimeter. Each flaring passage is connected with a source of lubricating fluid under pressure to deliver the lubricant to the mold. U.S. Pat. No. 3,448,788 issued June 10, 1969 to Keene et al is similar to the Gricol et al patent. It will be apparent that the resistance to flow decreases in the flaring passages leading to the mold in each of these two systems due to the increasing width of the gap passages as they approach the molds. Uniform distribution of lubricant along the full length of any side wall of the mold is dependent on the lateral expansion of the flow of lubricant. Such lateral expansion is substantially uncontrolled and thus cannot be insured and leads to non-uniform distribution of lubricant.
U.S. Pat. No. 3,556,197 issued Jan. 19, 1971 to Foye illustrates another system for lubricating a mold, this device is not for a process equivalent to the casting process for which the present invention is intended, but utilizes a gasket to define the passages interconnecting a manifold to a gap. The device of this patent will not provide the uniform distribution obtainable with the present invention.
Lubricating system currently used in the industry incorporates a pair of plates having opposed surfaces to define the lubricating gap leading to the molding passage around the complete circumference of the mold. The height of the gap and thus the cross sectional area of the gap is large particularly in relation to the cross section of the manifold supplying lubricant to the gap and results in relatively poor distribution of lubricating oil around the circumference of the mold.